Horrible Engine Rattle & Knock

LogixRat · February 3, 2004

As some of you might recall, I have whined a few times about having a rattle in my engine while under heavy acceleration. It was sporadic and hadn't occurred in quite awhile so I hadn't thought too much about it. Then the other day coming home from work, I went to pass some slow driving deadbeat that was in the fast lane, and lo and behold she sounded like she was gonna blow, the tranny shifted weird and the check engine soon light came on.

Also, about a week or so ago, I left my truck at work and drove a company vehicle home. It is a Ford diesel truck, and it was running and sitting next to my truck when I went to start up my own vehicle the next morning. Imagine my suprise when I get out of my truck and am confused why the knocking of MY truck is louder than the company truck that is a diesel!!!!

Anyhow, I took it to the shop, explained the whole ordeal and they did their "magic". I picked up the truck, talked to the dealer and they tell me it threw a P0300 misfire code. Says it occurred at 70mph/4500rpm/2nd gear. Perhaps that explains the weird tranny feel, so I ask if the tranny was okay. They tell me, it didn't throw a code, so there wasn't a problem there and no need to check it (yeah right!). Also, they cleaned my fuel injectors as they feel this is a "fuel related" problem.

So I'm on my way home, rather annoyed by the way, and I decide to hammer the living daylights out of her and see what happens. Hehe, well you guessed it. The rattle is back and the tranny is shifting weird. But you have to be 60mph+ and hit hard acceleration to get it to replicate. Still I have to be cautious when getting on the highway or passing someone in fear I will set off the rattle. And the rattle isn't the kind that happens and goes away after a second or two. It gets worse the longer you stay in it. And I got the check engine light to blink at me like before, so I setup another appointment for the stealership.

On the way to the shop this morning, I go to pass someone and the whole thing happens again but this time the engine light stays on. So now she is at the stealer, and I'm just curious what line they are gonna feed me now. Anyone know exactly what a P0300 code is, and how my truck might "misfire" w/o me hearing it? Any other ideas on what could be causing all this, especially with the tranny shifting? I am aware of GM's piston slap issue, and that might cause the knock...but the rattling is driving me nuts. I had a buddy with a Ford truck that had similiar noises, and ended up having to do serious engine work to his truck that cost out the ying yang. Luckily I'm still in warranty, barely at 33k, but I am having a hard time buying the fuel related problem. Suggestions???

Just confused, and getting rather annoyed.

Shaners · February 3, 2004

Mine threw a check engine code when towing this past December. There was alot of noise coming from under the hood, and it also happened while I was under heavier acceleration.

I never had the code checked... but I can tell you this. It happened the whole time I ran that tank of crappy gas from a "Pilot" truck stop. The next tank was a tankful of Texaco and the ping/rattle went away immediatly. I'm attributing it to "bad gas". (BTW it has never done it since).

Winston Ruddick · February 3, 2004

I agree with shaners. Try a different brand of fuel. I use only Esso gas (Canada) and find that if I stick with the same brand that my vehicles run a lot smoother.

LogixRat · February 3, 2004

Interesting you mention Texaco gas being better. The first thing the dealer asked me is if I had been running Texaco gas. I told him no, and he said good because they had been having problems with it. In my part of the world, Oklahoma, there are a plentiful supply of QT stores, who have their own "special blend" of gasoline and guarantees it. That is who I use, and that is who the dealer recommends. Of course, every once in a while I will have to fill up somewhere else, but that hasn't happened in several months.

Either way, you guys are saying this COULD be a fuel problem. I honestly did not believe that, and thought the dealer was simply trying to pull a fast one on me. I will at least listen to their prognosis with an open mind now.

Alas, I called around lunch time and they are still stumped at the problem. Apparently how the transmission is acting during the whole thing is something "new" to them. Sounds like I might be gett'n a rental tonight. I will know for sure here in a few minutes.

tmf6902 · February 3, 2004

Here is what my bible says about DTC p0300

Diagnostic Aids:

Runnnig the vehicle out of fuel causes sufficient misfire to set DTC p0300

Water contaminatnts in the fuel system can cause a single cylinder to misfire as well cause a random misfire

Restricted fuel filter

Excessive vibration from source other than the engine could cause misfire

-variable thickness brake rotor

drive shaft not balanced

certain rough road

and then they go on to expain how to diagnose something.

Shaners · February 4, 2004

Water contaminatnts in the fuel system can cause a single cylinder to misfire as well cause a random misfire

I honestly believe this was the problem I had with the "Pilot" truck-stop fuel....

I ran three tanks of fuel through the truck that day, and three different brands, and that was the only tank I had problems with.

silverado3500 · February 4, 2004

We had tons of QT stations in Atlanta. Unfortunately there aren't any here in Fort Walton Beach. Heh

LogixRat · February 4, 2004

Here is what my bible says about DTC p0300

Diagnostic Aids:

Runnnig the vehicle out of fuel causes sufficient misfire to set DTC p0300

Water contaminatnts in the fuel system can cause a single cylinder to misfire as well cause a random misfire

Restricted fuel filter

Excessive vibration from source other than the engine could cause misfire

-variable thickness brake rotor

drive shaft not balanced

certain rough road

and then they go on to expain how to diagnose something.

Woah....great info, thanks for sharing!! That is the written proof they were not feeding me a line of bull....I feel much better now. Still in yet, the stealership still has my truck. Apparently the tranny problem combined with the rattling is throwing them for a loop. After reading your post, my first thoughts was maybe a broken motor/tranny mount causing vibration in the driveshaft and maybe putting enough tension on the tranny to "bind" it from time to time and cause the slip.

Surely they have this info available to them, and better (at least I hope). What seems to worry me more than them is the SPORADIC gawd awful loud knock I will occassionally get. I understand a slight knock on startup is probably piston slap. To be louder than a diesel truck that is suppose to knock/chatter is rather excessive, at least in my opinion.

Honestly I am wondering if I shoudn't whine and moan, and see if GM will grant me the 100k warranty like I've been hearing so much about. My truck already has 33k on it, and knowing my luck my problem would come to haunt me at 37k or something stupid like that.

PS - I might add a little note here....they put me in a reg cab 04 with the 4.8 engine as my rental/loaner. Not too shabby at all. Although I know the 5.3 is a little stronger, the 4.8 is very powerful in the regular cabs. I can't hardly fathom the thought of the 5.3 in them...*drool*. Definitely the way to go for building a truck based around speed and performance.

LogixRat · February 6, 2004

Finally got my truck back yesterday (02.05.04), and she is running great!! I guess the stealership was on top of their game, even though I had my doubts. Apparently my catalytic converter had somehow broken down on the inside, which they replaced. Also, they put in a new O2 sensor.

I did find it unique that my cat would be malfunctioning and I asked them about it. I was told this WAS NOT an uncommon problem. Apparently it is a MANUFACTURING defect where stuff on the inside breaks lose. They made it sound like they have replaced LOTS of them. Not sure I liked hearing that, but at least they did fix the problem FREE OF CHARGE under my factory warranty. Thankfully, I haven't switched out to a custom exhaust yet, or it would have voided the whole thing and I would have had to pay out of pocket. By the way, emission warranty is 8 years/80k miles, and the cost to have GM fix my little problem was right at $1100 - again, thank goodness for the factory warranty.

Nonetheless, things are going great. And trust me....I have put it to the test.